Apparatus for extruding hollow articles



Feb. 6, 1945.

D. M L. FROTHINGHAM APPARATUS.FOR EXTRUDING HOLLOW ARTICLES 4 Sheets-Shet 1 Filed D80. 51, 1940 INVENTOR. Dow/up McL. F0771/A/6 mm AWOFNEYS.

11 M L. FRQTHINGHAM 2,368,980

APPARATUS FOR EXTRUDING HOLLOW ARTICLES Feb. 6, 1945.

Filed Dec. 31, 1940 4 Sheets-Sheet 2 IT M I l l :i i: /2 t I I I INVENTOR. Da/waw McL. FROTH/A/G/MM 477mm; YS.

Feb. 6, 1945. D. MOL. FROTHINGHAM 7 2,363,980

APPARATUS FOR EXTRUDING HOLLOW ARTICLES 4 Sheets-Sheet 3 Filed Dec INVENTOR.

"Illlllf'lb H4. & M U w IN m ,m Z A M m Feb. 6, 1945. D. M L. FROTHINGHAM 2,363,980 I APPARATUS FOR EXTRUDING HOLLOW ARTICLES Filed Dec. 31, 1940 4 Sheets-Sheei 4 I INVENTOR. .Da/wu 0 Me L. Hm THING/10H A TTORNE X5.

Patented Feb. 6, 19.45

UNlTED STATES PATENT OFFICE 2,368,980 APPARATUS FOR EXTRUDING HOLLOW ART ICLES Application December 31, 1940, Serial No. 372,598

3 Claims.

The present invention is directed to the forming by extrusion of articles with a hollow interior of predetermined contour. 2

It is known that articles may be extruded with a hollow interior by the use of a piercing mandrel to form a hole in the hollow slug which in turn is reproduced in the article after it has been extruded. Insofar-as I am aware there has been no method of extrusion by which the configuration of the interior of the article could be accurately controlled and reproduced in an indefinite number of articles.

It is desirable to form many varieties of extruded articles which are open at one end'and which are closed at the other end. Such articles may assume various shapes and the internal opening or bore may vary in contour in accordance with the uses to which the finished product is to be put.

Currently the extrusion of blanks for shells in' military ordnance work presents a large field "for the use of the apparatus of my invention.

The general object of the invention has been to provide an apparatus by which a new article of manufacture can be made which is characterized by an extruded shape with a hollow interior of;

a predetermined distance between the endo! the mandrel and the orifice. Still another object operates with the orifice to impart to the finished controlling the contour of that part or the plug article a hollow interior of the finished contour. In order to prevent premature extrusion through the orifice during the piercing operation a plug member is provided which seals the orifice until the piercing has been eflected. V

. It hasbeeniound that the end face or the extruded article may be controlled in'shape by which contacts. the slug, and this constitutes a part my invention. 7

The contour of the end of the bore in the article may likewise be controlled by providing the mandrel end with a predetermined contour and this likewise constitutes a part of the present I invention.

To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter fully described and particularly pointed out in the claims; the annexed i0 drawings and the following description setting forth in detail certain means and one mode of carrying out the invention, such disclosed means and mode illustrating, however. but one of various ways in which the principle of the invention may be used. c

In said annexed drawings- V Fig. 1 is a vertical section through an extrusion mechanism embodying the present invention showing the parts near the beginning of the extrusion stroke;

Figs. 2 and 3 are sections similar to Fig. 1 showing advanced portions of the extrusion cycle;

4 is a schematic showing of the hydrauliccontrol system employed;

2!! Fig. 5 is a section through the preformed-slug prior to'actualextrusion through the orifice Fig. 6 is a transverse section through an extruded article showing one end or the bore ta- .pered; and

Fig. 7 is a similar section bore at each end of the slug.

. Referring now to Fig. 1, there is provided an extrusion press embodying a bed i0 and a ram 12 movable toward and from the bed to perform the extrusion operation. The extrusion die mechanism is made in two parts which are adapted to nest together and include a ram carried portion and a portion supported on the bed.

In the preferred practice or my invention the extrusion is accomplished by the so-called indirect method, in which the die side walls and the end of the die carrying the mandrel are fixed with respect to each other. The portion of the mechanism in which the orifice is formed is slidingly received within the die to the end that the orifice and'the die side walls move relative to each other. The orifice mechanism is supported by the-ram and the die mechanism by the base, although it will be understood that this is the preferred 50 showing only and is vention'. v.

The die mechanism comprises a bed casting Ii which is hollow to receive a cylinder ll bolted tothe bed. A piston II for purp shereafter described is slidingly received in the cylinder and showing a tapered not intended to limit the in- I supports a piercing mandrel l9 threadingly received therein for easy replacement.

The die in which the mandrel functions is "formed, as indicated at 20, in a casting 22 which is bolted as at 23 to the casting IS. A tapered .plug 25 is received in the lower end of the die opening 20 and is provided witha central bore in which slides the mandrel l9.

To control the operation of the mandrel a second cylinder 28 is mounted within the casting l and communicates, as indicated by the piping 29, gzvith the upper side of the cylinder H to connect the same with the lower side of the cylinder 28. A control piston 30, including a piston rod 32, is slidingly received in the cylinder 28, the rod projecting above the level of the cylinder for a substantial distance to be engaged by an elenient of the ram mechanism hereafter described.

Itwill be noted that the piercing face of the mandrel is formed with a concave surface, as

indicated at 34, to the .end that the preformed slug will comprise a bore with a convex bottom as shown at 35 in Fig. 5, the function of which will hereafter be described.

The orifice mechanism which is supported by the ram is carried by a casting 40 which is bolted at 42 to the ram I2. This casting is provided with a cap 44 suitably secured'thereto and is bored and tapped asat 45.

-An orifice die member 41 is employed, the external diameter of which is such that it closely fits within the bore flLof the extrusion die. It is provided with a preformed end face 50 which engages the slug and defines an orifice through which the extruded slug is pushed, as shown in Fig. 2, to form a finished article similarto those shown in Figs. 6 and "I.

The preformed surface adjacent the die orificeis best indicated by the complementary surface of which is to cause it to completely fill the space between the two and is bounded by the wall 20, to result in a preformed slug of the shape shown in Fig. 5. It is after the'formation of this shape a that the actual extrusion is effected.

The preformed slug of Fig. 5 will be seen to have a concave upper portion 55, which extends across the entire distance from one edge of the orifice lip to the other. This shape, provided for respect to the die orifice member 41 to form with,

' it a generally convex end for the. slug with a centrally disposed concave portion To accomplish 62 to permit the plug to be pushed upwardly by the forming article, as shown in Fig. 2. It is to be noted in this connection thatthe internal opening in the orifice member 41 is generally a little larger in diameter than the extrusion orifice, thus preventing friction contact with resulting wear between the article as it is formed and the member 41. 7

- Control of the distance between the mandrel end and the orifice is accomplished through the operation of a bar 65, which is threadingly received at 66 in the casting 40 and is braced with respect thereto by the rib member 68 As the ram descends the bar will come into contact with the piston rod 32 heretofore described to actuate the piston 30 to control the mandrel, the exact point at which the bar and rod will come in contact is adjusted by a bolt "and a lock nut -'|l carried by a rod 32. As hereafter described, the present'invention is predicated upon maintaining a controlled distance between the end of the mandrel and the edge of the extrusion orifice, a. distance which is indicated in Fig. 5 by the letter X and the associated arrow. In order to extrude an article in accordance with the present invention there must be provided some means to ascertain that the distance at thev beginning of the extrusion stroke, as well as at all points therein, is accurately known. It is not sufllcient to: merely move the orifice member 41 and the mandrel 19 toward each other until the slug is pierced to a predetermined point or until a form similar to that of Fig. 5 is obtained, at which time an external pressure will be set up as distinguished from the pressure required to fill up the air spaces within the die unit. If every slug placed within the dies was uniform the controls outlined above would be satisfactory. Since, however, the invention is employed withsawn-ofl pieces of billets it is obvious that the over-all length cannot be-accurately controlled, nor can the cross-sectional dimensions be known unless methods prohibitive in cost are employed to form the slug. Accordingly, in thepractice of my invention I pierce with the mandrel until adistance X is obtained between the end of the mandrel and the end of the orifice. I..then continue the closing movement of the die members to how the material throughout all the die spaces and build up the extrusion pressure while maintaining this distance X constant. This is done by retracting the mandrel at a speed exactly equal at the same speed at which the ram supporting this purpose the plug is supported by a'piston 58, which is received in a hydraulic cylinder 60. Due

to the application of fluid pressure within the cylinder 60. the plug is held in the position in;

dicated.

pressure just mentioned N releasedthrough a port 6| which is controlle .by valve mechanism member 41 is moved the under area of the piston 30 and the top area of the piston l8 are equal.-

This results 'in displacement of oil-from the cylinder 28 to the cylinder through the pipe 30 s'uchlthat the increase in displacement in the latter cylinder is always equal to the decrease in I displacement in the cylinder 28.

It is well to point out here that the mandrel l9 and its related piston 18 are supported 'during the piercing operation by hydraulicpressure on the under side of the said. Distonwithin the cylinder I! and this pressure must be released when the mandrel is forced downwardly.

To thus control the, piston 18 alimit switch I5 is engaged by therod 32 at the instant it starts its downward movement. operates I as the piston 39 descends it may push the piston l8 downwardly, pushing oil out of the opening 18 back into the tank 80. When the extrusion stroke has ended and the ram begins to rise the downward pressure on the rod 32 will be removed. At this time the air in the tank 88 will force oil back through the opening 18, raising the piston l8 and the mandrel l9 to their' initial positions.

As the piston l8 rises oil is forced back beneath the piston 39, raising the rod 32 to its initial position whereupon the limit switch will be again actuated to close the valve 16, retainin the mandrel in an elevated position until the punch again descends to bring th bar 65 and rod 32 in contact.

As indicated above, by the use of the equipment thus 'far described it is possible to move the mandrel downwardly at. a constant rate, which, however, is dependent upon the position of the ram. I shall now describe mechanism by which the mandrel may be controlled independently of the position of the ram and its corresponding orifice member 41 to vary the distance X between the orifice and the end of the mandrel." Such mechanism is shown in Fig. 4.

Referring to that figure it will be seen that there is provided a cylinder 85 which carries a piston- 86 supporting a cam plate schematically the actual extrusion begins by the opening of the valve 8 2 above the plug to release the same and permit the passage of th plastic material through the orifice. As the piston 38 continues its further descent a vacuum will be created above the piston, allowing oilto flow thereto out of the cylinder 85. A constant fluid pressure applied to the piston 86 through the passage ill! from any suitable source will then move the piston and its associated cam plate toward the left, Fig. 4. This will cause a pair-of rollers H2 and 3 of the link mechanism to travel toward or away'f-rom each other, depending on the contour of the cam follower surfaces. This in turn will actuate the piston 94 to either increase or decrease, or held constant, the volumetric capacity between the piston and the cylinder 93. -As

. above indicated, this acts to control the rate of shown at 88. The cam plate is formed with, a

pair of follower surfaces 98 and 9|.

Associated with the aforementioned mechanism is a second cylinder 93 with a piston 94 support; ed therein. Therpiston 94 is operatively connected with four links 95A, 95B, 95C and 95D, which are pivotally mounted with respect to each other to form a parallelogram. The link pivot opposite to the piston 84 is fixedly supported at 91 with respect to the foundation.

The hydraulic system by which the lower portion of the cylinder 28 and the upper portion of the cylinder I! are connected includes'a further .connection III! with the cylinder 93. A valve I2 is interposed in this line. It will be apparent, however, that if the piston 94 is displaced during the downward travel of the piston 30 a To'control the relativ position of the piston 94 an oil line I85 is provided which connects through a three-way valve I08 from the cylinder 85 to the cylinder 28 on top of the piston 30. This valve is normally connected to an oil reservoir and during the'mandrel travel prior to extrusion the upper part of the cylinder 28 is receiving oil from this reservoir." When actual.

movement of the mandrel H! with respect to the orifice member".

It will be understood that the die contour In general, this type of cam plate will result in the shape shown in Fig. '7 where the central portion of the bore is uniform in diameter and each end is tapered.v Fig. 6 shows an extruded .blank adapted for use in shell makin where the bore is of constant diameter except at the inner end where it is tapered. Such a shape would require a cam plate with a pair of diverging side walls followed by a section with-side walls which are parallel with each other. Many other shapes may be made under the present invention and these shapes may each'be controlled by providing a predeterminedrcontour for the cam plate 88.

As heretofore stated, it is desirable to finish the blanks as shown in Fig. 6, with a generally square end at the right and to provide the bore with a generally flat bottom. It has been found that by shaping the preformed blank of Fig. 5 with a convex surface 35 and the concave surface 55 this result will follow. As the central body of material between the two sin-faces tends to fold out during extrusion, the degree of v squareness in the blank end is controlled by the depth of the concavity 55, and likewise the degree of convexity in the surface 35 controls the shape of the end of the bore.

In making projectiles and similar articles to be loaded with high explosive an ultimate object is'to provide an'outer casing which will break up into small pieces when the charge is exploded. This fragmentation may be accurately controlledwith my inventionby forming intersecting lines of weakness throughout theexj truded article. Then when the shellexplodes it will .breakup along these lines of weakness much in the manner a hand grenade bursts due toits' checkerboard exterior. T This result is obtained by employing, fluted mandrel which will form the interior bore of the d ,7 article with a series of longitudinally extending extrusion starts the three-way valve disconnects to pass to cylinder 28. The two valves I82 and 188. are solenoid controlled to be opened at the ridges and valleys to produce an effect analogous. to corrugation. e

A series of axially; extendingannular tions is provided by alternately sharply increasing and decreasing the, internal diameter of the instant the extrusion pressure is; built up and to here. This may be accomplished byoscillating orifice member 41.

the mandrel l9 during the extrusion operation to alternately increase and decrease the value of the distance X. Such oscillation may be secured by incorporating within the mandrel construehollow shapes, together with an improved shape which results in a product capable oi! wide usage.

Other forms may be employed embodying the features of my invention instead of the one herein explained, change being made as regards the means and the steps herein disclosed proto thereby control the relative position of said mandrel with respect to. its supporting die member,

2. In apparatus for extruding hollow articles, a pair 01' die members mounted for movement relative to each other to effect an extruding oporation, an extrusion orifice formed in one of said members, a plug member adapted'to tempovided the elements stated by any 01' the following claims or the equivalent of such stated elements be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In apparatus for extruding hollow articles.

a pair of die members mounted for movement relative to each other to eiIect an extruding operation, an extrusion orifice formed in one of said members, a piercing mandrel mounted in the other of said die members and mounted for axial movement in alignment with the orifice of.

rarily seal said orifice, an hydraulic cylinder and piston in alignment with said plug with said plug and said piston acting to moveas a unit, a piercing mandrel mounted in the other of said die members and mounted for axial movement in alignment with the orifice of said first die member, an hydraulic cylinder in alignment with said mandrel, an extension on said mandrel forming a piston in said last-named cylinder, a-

third hydraulic cylinder interconnected with said last-named cylinder, a piston in said third cylinder mounted to be actuated upon relative movement between said two die members to force liquid from said third cylinder into said lastnamed cylinder to thereby control the relative position of said mandrel with respect to its supporting die member.

a; In apparatus for extruding hollow articles,

, a pair of hollow die members mounted for movement relative to each other to eflect an extruding operation, an extrusion orifice iormed in one of said members, a piercing mandrel mounted in the other of said die members, ram means to eii'ect relative movement between said die memsaid first die member, an hydraulic cylinder in alignment with said mandrel, an extension on said mandrel forming a piston in said cylinder, a'second hydraulic cylinder interconnected with said cylinder, a piston in said second cylinder mounted to be actuated upon relative movement between said two die membersto force liquid .rrom said' second cylinder into said first cylinder bers, means responsive to said relative movement to move said mandrel and the die member having said extrusion orifice with respect to said other die member at the same rate of speed and means capable of varying the distance between said orifice and said mandrel independently of the position of said ram.

7 MCL. FROTHINGHAM. 

